Data transfer can be performed with the following steps:
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(1)Tap the "MENU" on the app screen bottom right
(2)Tap "DATA TRANSFER"
(3)Tap "TRANSFER SETTINGS"
(4)Register your password (you may create your own password)
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※Memory Diamond you have will not be transferred when transferring data between different OS (Android to iOS or iOS to Android).

Try obtaining gears while your inventory is at limit and you will be able to use Memory Diamonds to increase the amount of gears you can hold.
You can also sell gears to open up space in your inventory.

If all your characters are defeated you can use Memory Diamond to continue, but the number of times you can continue differ depending on the quest.
Also, how many characters you can recover is different for each quest.
If you cannot continue, please check the number of Memory Diamonds you have and the number of times you continued.

Depending on the character’s attack stat and the enemy’s strength you might not be able to deal damage.
If you are having difficulty defeating the enemy, power up your character and equipment before challenging.

If you cannot follow due to limit, either the number of followers of the player you wish to follow has reached the limit, or the number of players you are following has reached the limit.

The current number of followers and follows can be checked.

【MENU】→【FRIEND】→【FRIEND LIST Screen bottom】

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Followers：Number of players who are following you (Maximum 1000).
Follow：Number of players you are following (Initially 5, but the limit will increase depending on the Rank)
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Also regarding follow, you can remove the players that are shown on the Follow Screen of the Friend List.